1. Field of the Invention
The present invention relates generally to the field of secure transmission of content such as software, music, and movies through public communications networks. More particularly, the invention relates to receiving encrypted content with a first encryption through a public communications channel and atomically re-encrypting it for private, local use with a second encryption.
2. Description of the Related Art
Many different approaches have been taken to prevent unauthorized reproduction and distribution of content such as movies and videos, music, software, and television programming. Most of these approaches have focused on one of two areas of vulnerability of the content. The first area is the distribution of content to the end customer. Cable and satellite broadcasters, for example, broadcast almost all programming with encryption. The keys to the encryption are sent to a set-top box that receives the encrypted broadcast data, decrypts it, and forwards it to playback or recording devices (e.g., televisions (TVs), video cassette recorders (VCRs)). Similarly, for software distributed over a public channel such as the Internet, the software is frequently encrypted prior to the transmission between the server and the client, then decrypted upon receipt by the client and installed into the computer in an unencrypted form. In another example, for DVD's (Digital Video Disks or Digital Versatile Disks) there is an encryption format embedded into the disk that is decrypted by the DVD player. The unencrypted signal is then conveyed to playback or recording devices.
All of these systems allow for the transmission channel or media to be reasonably secure. Typical unauthorized users receiving broadcasts of cable or satellite television programs or intercepting such communications on the Internet, are frustrated by the encryption that is maintained over the radio or wired link. However in all of these systems, once the signal has been received and decrypted by a receiving device, it is then “in the clear” and available for copying, reproduction and distribution (at least some of which may be unauthorized, depending on the rights associated with the data by the content owner).
The second area of the vulnerability is the use of the content after receipt by the end customer. Several different efforts are aimed at protecting against unauthorized reproduction and distribution of copyrighted content after it has been obtained by a user or consumer. Content Protection for Recordable Media (CPRM) was jointly developed by Toshiba, Intel Corporation, IBM and Matsushita to allow consumers to store and replay the extensive range of music content that is becoming available through electronic music distribution platforms. CPRM allows music to be recorded on a portable music player, such as an MP3 player, but prevents the unauthorized reproduction and distribution of the music. High-Bandwidth Digital Content Protection (HDCP), developed by Intel Corporation, protects digital content as it is transmitted between a set-top box or player to a display or playback or recording device. Like CPRM, HDCP allows a user to enjoy and use the encrypted content, but prevents unauthorized reproduction and distribution. Digital Transmission Content Protection (DTCP,) developed by a consortium of hardware manufacturers, allows a broadcaster to include a copy control code in content to control the number and types of copies that can be made to the content.
In each of these systems, the content is decrypted at some point in the distribution chain and at that point becomes vulnerable to unauthorized reproduction and distribution. If the device receiving the content is a flexible software-driven box such as a personal computer (PC), then the software that performs the decryption, as well as the content, may be easily accessible to users that may attempt to produce unauthorized copies. This leaves the content vulnerable, notwithstanding the various efforts that have been applied to encrypt and protect it farther upstream in the content distribution model.